WO2010031430A1

WO2010031430A1 - Circuit arrangement and method for operation of a discharge lamp

Info

Publication number: WO2010031430A1
Application number: PCT/EP2008/062358
Authority: WO
Inventors: Alois Braun; Walter Limmer; Maximilian Schmidl
Original assignee: Osram Gesellschaft mit beschränkter Haftung
Priority date: 2008-09-17
Filing date: 2008-09-17
Publication date: 2010-03-25
Also published as: KR20110056546A; EP2327276B1; JP5542824B2; US20110169427A1; US8531122B2; CN102160467B; JP2012503270A; CN102160467A; TW201014469A; EP2327276A1

Abstract

The present invention relates to a circuit arrangement for operation of a discharge lamp, comprising: an input having a first input connection (E₁) and a second input connection (E₂) for connection of a supply voltage; a first electronic switch (Q₁), which has a control electrode, a working electrode and a reference electrode, wherein the working electrode is coupled to the first input connection (E₁); a first diode (D₁), the anode of which is coupled to the second input (E₂) and the cathode of which is coupled to the reference electrode of the first electronic switch (Q₁) to form a first junction point (N); a control apparatus (12), which is coupled to the control electrode of the first electronic switch (Q₁) in order to drive said first electronic switch (Q₁); an output with a first output connection (A₁) and a second output connection (A₂) for providing an output voltage (U_A) to the discharge lamp (La); an inductance (L_z), which is arranged in series with one of the output connections (A₁; A₂); a lamp inductor (L₁), which is coupled between the first junction point (N) and the first output connection (A₁); and a first capacitor (C₁), which is coupled between the first output connection (A₁) and the anode of the first diode (D₁); wherein the control apparatus (12) is designed to switch the first electronic switch (Q₁) on continuously for a switched-on time and to switch it off continuously for a switched-off time; wherein the circuit arrangement furthermore comprises a voltage measurement apparatus (10) for measuring the output voltage (U_A), wherein the voltage measurement apparatus (10) is designed to produce at its output a signal which is correlated with the measured output voltage (U_A) wherein the voltage measurement apparatus (10) is coupled to the control apparatus (12) in order to transmit this signal to the control apparatus (12), and wherein the control apparatus (12) is designed to vary the switched-off time (T_off) as a function of the measured output voltage (U_A). The invention furthermore relates to a corresponding method for operation of a discharge lamp.

Description

Confession

Circuit arrangement and method for operating a discharge lamp

Technical area

The present invention relates to a circuit ^arrangement for operating a discharge lamp, comprising an input having a first and a second input terminal for connecting a supply voltage, a first electronic switch having a control electrode, a working electrode and a reference electrode, wherein the working electrode is coupled to the first input terminal, a first diode whose anode is coupled to the second input terminal and whose Ka ^¬ method is coupled to form a first connection point with the reference electrode of the first electronic switch, a control device for the control of the first electronic switch is coupled to its control electrode, an output having a first and a second output terminal for providing an output voltage to the discharge lamp, an inductance, which is arranged in series with one of the output terminals, a lamp string el, which is between the first connection point and the first output terminal gekop ^¬ pelt, and a first capacitor coupled between the first output terminal and the anode of the first diode, wherein the control device is designed, the first electronic switch continuously conducting for a switch- and not switch ^¬ for a turn-off time. It also relates to a corre ^¬ sponding method for operating a discharge lamp. State of the art

Such a circuit arrangement is known from the prior art. It is essentially a buck converter with a downstream ignition device for the discharge lamp, the mentioned inductance representing the ignition inductance. In practice, it has now been found that discharge lamps which are operated on such a circuit arrangement sometimes go out. By introducing additional ohmic resistors in the output circuit, d. H. Serial to the discharge lamp, the extinction could be largely prevented. However, this solution is undesirable in view of the resulting power loss.

Presentation of the invention

The object of the present invention is therefore, an aforementioned circuit arrangement relate hung as an aforementioned method in such a wei ^¬ terzubilden that an extinction of the discharge lamp with low power dissipation is reliably prevented.

This object is achieved by a circuit arrangement having the features of patent claim 1 and by a method having the features of patent claim 14.

The present invention is based on the finding that vibrations can occur in the output circuit as a function of the starting inductance and the first capacitor. At low lamp impedances they are little dampens loaded and can interfere with the lamp operation, as the Lam ^¬ penstrom swings. In the usual further wiring of a known from the prior art, generic ßen circuit arrangement, a measurement of the output current is provided, wherein by appropriate control of the first electronic switch, the output current fixed-frequency peak-to-peak is regulated. Now enters a vibration on in the output circuit, so that can to füh ^¬ ren that duty cycles fail completely, and the effective drive frequency of the resonance frequency which is essentially determined by the Zündinduktivität and the first capacitor approaches. The control loop thus "drags itself into oscillation." In doing so, the current can even swing into negative, causing the lamp to extinguish.

The known from the prior art approach of inserting ohmic resistors in the output circuit was unknowingly used to dampen the vibration, but led to undesirably high power loss.

On the basis of these findings of the products contained ^¬ constricting invention eliminates the above problem in that the circuit arrangement is not operated in nearly fixed frequency in the continuous mode, but the turn-off of the first electronic switch is varied. By measuring the output voltage, the distance to the mentioned resonant frequency is determined and a sufficient distance is established by varying the switch-off time. This reliably prevents a "pulling in" of the control loop into the oscillation, as a result of which extinction of the discharge lamp can reliably be prevented even without the use of additional ohmic resistors for damping the output circuit. The control device may be adapted to the switch-off proportional, in particular directly or indirectly, per ^¬ proportional to vary the output voltage. The control device may in particular be designed to shorten the turn-off time when the output voltage increases, and vice versa. If T _e i _n the on time T _of the turn-off, _{L, for} the serially represents one of the output ^¬ connections arranged inductance and C the capacitance of the first capacitor, the rudder systems particularly adapted to vary the switch-off such that applies :

- / a ~ * ~ - / off

By varying the turn-off time, the control device particularly preferably avoids a range of 20 percent below to 20 percent above the resonance frequency, so that the following applies:

To ensure that even harmonics of the resonance frequency are avoided, the following also applies:

Again, it is particularly preferred in this context if a range of 20 percent below to 20 percent above the respective frequency is avoided, so that the following applies:

7 1

Bis 0.8 to 1.2 * ^ =; n = 1, 2, 3, ... n * {Teιn + Taus) 2 ^ _Z ^C ₁ In particular, when the impedance of the to be connected at the output ^¬ sequent discharge lamp is not negligible, in the respective above-mentioned formula, the detuning of the resonant circuit of the first capacitor and the home is productivity taken into account by the impedance of the output to be connected ^¬ sequent discharge lamp. Thus, very precise values for unavoidable Fri ^¬ sequences can be determined and considered in the control of the control device.

A circuit ^arrangement according to the invention preferably further comprises a current measuring resistor, which is coupled between the anode of the first diode and the second input terminal, for measuring the current through the first electronic switch in its conducting state, wherein the control device is coupled to the current measuring resistor and is designed to vary the switch-on time for regulating the current to a predefinable value. The switch is in particular so-regulates ^¬ that the average current remains constant despite the different chen off times.

The aforementioned embodiments of a circuit arrangement according to the invention relate in particular to realizations with a single electronic switch. However, the idea on which the present invention is based can, in particular, also be applied to a full-bridge topology. To that extent, a preferred far Erbil ^¬ dung of a circuit arrangement according to the invention further comprises a second, a third and a fourth electronic switch, wherein the first, second, third and fourth electronic switches represent a whole ^¬ bridge, wherein the first connection point egg represents NEN first bridge center point, wherein the scarf ^¬ processing arrangement further includes a second diode coupled in parallel with the first electronic switch, wherein the second electronic switch is coupled in parallel with the first diode, wherein the third and fourth electronic switches to form a second connection point representing a second Brückenmit ^¬ core; the coupled together, wherein the second bridge center point represents the second output terminal, wherein the control device is designed, the first, second, third, and according to the invention to control the fourth electronic switch. The control device controls the third electronic switch is preferably implemented in a ers ^¬ th phase-conductive, non-conductive to turn off the fourth electronic switch and the first electronic switch, in a second phase, the fourth electronic switch conductive, the third electronic switch and the second electronic Switch non-conducting switch, wherein the first and the second phase with a first vorable ^¬ frequency, which is in particular in Niederfrequenzbe ^¬ rich continuously alternate, the control device is further designed in the first phase, the second electronic switch and in the second phase, the first electronic switch with a second predetermined frequency, which is rich in particular Hochfrequenzbe ^¬ rich, alternately conductive and non-conductive switch and thereby to vary the turn-off in dependence on the measured output voltage.

In each case, a free-wheeling diode is connected in parallel to each of the third and fourth electronic switches. Further preferably, the circuit arrangement comprises a second capacitor, which is coupled between the first input terminal and the first output terminal. In this case, in the above equations, instead of the capacitance of the first capacitor, the total capacity of the first and second capacitors should be set.

Further preferred embodiments emerge from the subclaims.

The preferred embodiments presented with reference to a circuit arrangement according to the invention and their advantages apply correspondingly, as far as applicable, to the method according to the invention.

Short description of the drawing (s)

In the following, embodiments of the invention will now be described in detail with reference to the accompanying drawings. Show it:

Figure 1 is a schematic representation of a first embodiment of a circuit ^¬ arrangement with an electronic switch.

Fig. 2 is a schematic representation of a second exemplary embodiment of an inventive circuit arrangement with ^¬ full bridge topology;

3 shows the time profile of various currents in a peak-to-peak control according to the prior art; and

Fig. 4 shows the time course of corresponding quantities at resonance according to the prior art. Preferred embodiment of the invention

Fig. 1 shows a schematic representation of a first embodiment of an inventive Schaltungsanord ^¬ tion. This comprises an input with a first egg and a second input terminal E ₂ , to which a supply voltage can be connected. Between the inputs, an optional capacitor C _{E is} arranged, which serves to stabilize the input voltage. The circuit arrangement comprises a first electronic switch Qi with a control electrode, a working electrode and a reference electrode. The working electrode is coupled to the first input terminal E ₁ . Wei ^¬ thermore, attention must a diode Di, yet whose cathode is coupled with the formation of a connection point with the N Bezugselekt ^¬ rode of the electronic switch Qi. The circuit arrangement further comprises an output with a first Ai and a second output terminal A ₂ , at which an output voltage U _{A is provided} to a discharge lamp La. Between the connection point N and the first output terminal Ai, the series connection of a lamp inductor Li and an ignition inductance L _{z is} arranged. The connection point between the Lampendros ^¬ sel Li and the Zündinduktivität L _z is coupled via a capacitor ^¬ Ci with the second output terminal A ₂ . The anode of the diode Di is also coupled to the output terminal A ₂ .

For measuring the output voltage U _A , a voltage ^¬ measuring device 10 is provided. A quantity which is correlated with the measured output voltage U _A is coupled to a control device 12 which is coupled to the control electrode of the electronic switch Qi. to control this. The controller 12 is also coupled to a current measuring device 14, which is the voltage across a current sensing resistor R _s, the interim ^¬ rule the anode of the diode Di and the second inlet connection E _{2 are} coupled, measures, and to the Steuervorrich ^¬ tung 12 provides. Dashed lines show a firing capacitor C _zi . The control device 12 is designed according to the invention to vary the switch-off time of the switch Qi as a function of the measured output voltage U _A. The variation takes place in particular in such a way that the frequency with which the switch Q _{x is} driven differs from a resonance frequency and its multiples, which are essentially defined by the ignition inductance L _z and the first capacitor Ci. The current flowing through the lamp inductor L _x is denoted by I _Li , the current flowing through the lamp La is denoted by I _La, and the current flowing through the switch _Q i is denoted by I _Q i.

2 shows a schematic representation of a second exemplary embodiment of a circuit arrangement according to the invention, wherein the circuit arrangement now has a full bridge topology. Reference numerals that have been introduced in co ^¬ menhang with Fig. 1, are used for like and identical components of Fig. 2 and will not be further inserted again.

This further comprises a second Q ₂ , a third Q ₃ and a fourth switch Q ₄ . The switch Qi is a second diode D _{2 connected in} parallel. Between the first input terminal Ei and the first output terminal Ai, a second capacitor C _{2 is} coupled. Between the first switch Qi and the second switch Q ₂ is a first bridge center BM 1, between the third Switch Q ₃ and the fourth switch Q _4, a second bridge center BM2 formed. The productivity Zündin ^¬ L _z between the second output terminal A ₂ and the second bridge center point BM2 presently is located. Optionally, a further ignition capacitor C _{z2 is} shown, which may be provided as an alternative or in addition to the ignition capacitor Czi. This can be coupled in parallel to the two output terminals Ai, A ₂ .

The operation of the circuit arrangement of FIG. 2 is effected by corresponding control of the switches Qi to Q ₄ by the control device 12. In this case, the control device 12 controls the switch Q ₄ in a first phase, the switches Q ₃ and Q ₂ non-conductive. In a two ^¬ th phase, the switch Q _{3 is turned on} , the switches Q ₄ and Qi non-conductive. The first and second phase change continually with a first vorgeb ^¬ cash frequency lying in particular in the low frequency region decreases. In the first phase, the switch Qi and in the second phase of the switch Q ₂ with a second predetermined frequency, which is in particular in Hochfrequenzbe ^¬ rich, alternately turned on and non-conductive ge ^¬ . In this case, the turn-off time is varied in dependence on the measured output voltage U _{A in} such a way that the drive frequency differs from the resonance frequency, which is essentially defined by the capacitances Ci, C ₂ and the ignition inductance L _z , and their multiples.

Figures 3 and 4 illustrate again the considerations and findings underlying this present invention. For the basic topology of Fig. 2 - but without control according to the invention - 3 shows the time profile of various currents in a peak-to-peak regulation of the current I _Q i through the switch Qi. Shown is a Abschaltstromschwelle I _s . As soon as the current through the switch reaches this current value I _s , the switch I _Q i is switched to the non-conducting state. The turn-on time is T _e i _n and leads to the increase of the current I _L i by the Lampendros ^¬ sel Li. After switching off the switch Qi, ie in the demagnetization phase of the lamp inductor Li, the current through the lamp inductor I _L i decreases continuously, see T _off . Furthermore, the current I _D1 is drawn in the freewheeling phase, ie with the switch Q ₁ open. Finally, the supplied to the discharge lamp La current I _La , which corresponds to the average current I _L i _qUer through the lamp inductor L ₁ is entered.

Fig. 4 shows the situation when an oscillation occurs in the output circuit, ie the output current I _La . Occurs ei ^¬ ne vibration to the output circuit, the current obtained by the current measuring resistor R _s at the maximum of vibration an "offset", that is, the off time is reached earlier and at first the on-time decreases tem- At the minimum of the vibration T _e is i _n as usual, ie at least more energy is coupled in at the minimum than at the maximum, in particular energy is coupled in with the natural frequency of the oscillating circuit from the starting inductance L _z and the capacitor Ci, C _2. As a result, the circuit oscillates, the offset increases at the maximum, until it is so high that the switch-off threshold is already reached at the switch-on time, see ti of Fig. 4, of the switch Q. Thus, the switch Qi no longer turns on.The total energy is coupled in the minimum, the circle is excited with its resonant frequency. In other words, the control loop "pulls itself into the vibration".

Claims

claims

A circuit arrangement for operating a discharge lamp, comprising:

- An input with a first (Ei) and a second input terminal (E ₂ ) for connecting a supply voltage; a first electronic switch (Qi) having a control electrode, a working electrode and a Be ^¬ zugselektrode, wherein the working electrode is coupled to the first input terminal E _1); - A first diode (Di) whose anode is coupled to the second input terminal (E ₂ ) and whose Ka ^¬ method is coupled to form a first connection ^¬ point (N) with the reference electrode of the first e- lektronischen switch (Qi); - A control device (12) which is coupled to drive the first electronic switch (Qi) with its control electrode;

- An output having a first (Ai) and a second output terminal (A ₂ ) for providing an output voltage (U _A ) to the discharge lamp (La); an inductance (L _z ) serially connected to one of the output terminals (Ai; A ₂ ); a lamp inductor (Li) coupled between the first connection point (N (and the first output terminal (Ai);

a first capacitor (Ci) coupled between the first output terminal (Ai) and the anode of the first diode (Di); wherein the control device (12) is adapted to keep the first electronic switch (Qi) for turning on a turn-on time and nonconducting for a turn-off time; characterized in that the circuit arrangement furthermore comprises a voltage measuring device (10) for measuring the output voltage (U _A ), wherein the voltage measuring device (10) is designed to provide a signal at its output which ^matches the measured output voltage (U _A ), wherein the voltage measuring device (10) for the transmission of this signal to the control device (12) to the control device (12) is coupled, and wherein the control device (12) is designed, the off time (T _off ) depending on ge ^¬ measure output voltage (U _A ).

2. Circuit arrangement according to claim 1, characterized in that the control device (12) is designed to vary the turn-off time (T _off ) proportionally, in particular directly or indirectly proportional, to the output voltage (U _A ).

3. Circuit arrangement according to claim 2, characterized in that the control device (12) is designed, at ei ^¬ ner enlargement of the output voltage (U _A ) to shorten the turn-off time (T _off ) and vice versa.

4. Circuit arrangement according to one of the preceding claims, characterized in that in that the control device (12) is designed to vary the switch-off time (T _out ) in such a way that

where Tein represents the on time, T _off the off time, L the inductance (L _z ) arranged serially to one of the output terminals (Ai; A ₂ ), and Ci the capacitance of the first capacitor (Ci).

5. Circuit arrangement according to one of the preceding claims, characterized in that the following applies:

¹ - ≠ 0.8 to 1.2 * - ¹ lein 'l from ^^ y ^ Z ^ l

6. Circuit arrangement according to one of claims 4 or

5, characterized in that

≠,; n = 1, 2, 3, ...

"- \ 1 a ^ 1 ausJ

7. Circuit arrangement according to Claim 6, characterized in that the s

; n = 1, 2, 3,. , ,

8. Circuit arrangement according to one of claims 4 to 7, characterized that in the respective formula the detuning of the resonant circuit from the first capacitor (Ci) and the inductance (L _z ) by the impedance of the discharge lamp to be connected to the output (La) is taken into account.

9. Circuit arrangement according to one of the preceding claims, characterized in that it further comprises a current measuring resistor (R _s ), which is coupled between the anode of the first diode (Di) and the second input terminal (E ₂ ), for measuring the current by the first electronic switch (Q _x ) in its conducting state, wherein the control device (12) is coupled to the current measuring resistor and adapted to vary the on-time (T _e i _n ) for regulating the current to a predefinable value.

10. Circuit arrangement according to claim 9, characterized in that the circuit arrangement further comprises a second (Qi), a third (Q ₄ ) and a fourth electronic switch (Q ₃ ), wherein the first (Q ₂ ), the second (Qi) , the third (Q ₄₎ and the fourth electronic ^¬ specific switch (Q ₃₎ represents a full-bridge, said first connection point (N) represents a first bridge center point, wherein the circuit arrangement further comprises a second diode (D _2), which is parallel to first electronic ^¬ rule switch (Q ₂ ) is coupled, wherein the second electronic switch (Qi) parallel to the first diode (Di), the third (Q ₄ ) and the fourth electronic switch (Q ₃ ) being coupled to form a second connection point representing a second bridge center, the second bridge center representing the second output connection (A ₂ ) , wherein the Steuervor ^¬ direction (12) is designed to control the first (Q2), the second (Qi), the third (Q ₄ ) and the fourth electronic switch (Q ₃ ).

11. Circuit arrangement according to claim 10, characterized in that the control device (12) is designed, in a first phase, the third electronic switch (Q ₄ ) conductive, the fourth electronic switch (Q ₃ ) and the first electronic switch (Q ₂ ) nonconductive switch, in a second phase the fourth electronic switch (Q ₃ ) conductive, the third electronic switch (Q ₄ ) and the second electronic switch (Qi) non-conductive, wherein the first and the second phase with a first predetermined Frequency, which is in particular in the low frequency range, continuously alternate, wherein the control device (12) is further designed, in the first phase, the second electronic switch (Qi) and in the second phase, the first electronic switch (Q ₂ ) with a second predetermined frequency , which lies in particular in the high-frequency range, alternately conducting and nonconductive switching. and thereby to vary the turn-off time as a function of the measured output voltage.

12. Circuit arrangement according to one of claims 10 or 11, characterized in that the third (Q ₄ ) and the fourth electronic switch (Q ₃ ) each have a freewheeling diode is switched parallelge ^¬ .

13. Circuit arrangement according to one of the preceding arrival claims, characterized in that the circuit arrangement further comprises a second capacitor (C ₂ ) which is coupled between the first input terminal (Ei) and the first output terminal (Ai).

14. A method of operating a discharge lamp on a circuit arrangement having an input with a first (Ei) and a second input terminal (E ₂ ) for connecting a supply voltage; a first electronic switch (Q1) having a control electrode, a working electrode and a reference electrode, the working electrode being coupled to the first input terminal (Ei); a first Di ^¬ ode (Di) having its anode connected to the second inlet connection (E ₂₎ is coupled and whose cathode under

Formation of a first connection point (N) with the

Reference electrode of the first electronic switch

(Qi) is coupled; a control device (12) for driving the first electronic switch (Qi) is coupled to its control electrode; an output with a first (Ai) and a second starting connection (A ₂₎ for providing an output ^¬ voltage (U _A) to the discharge lamp (La); an inductance (L _z ) arranged serially to one of the output ^terminals (Ai; A ₂ ); a lamp choke

(Li) coupled between the first connection point (N) and the first output terminal (Ai); and a first capacitor (Ci) connected between the first output terminal (Ai) and the anode of the first diode

(Di) is coupled; wherein the control device (12) is adapted to control the first electronic switch (Q _x) for a continuously conductive switch and for egg ^¬ ne off to switch non-conductive; characterized by the following steps: a) measuring the output voltage (U _A ); b) coupling a signal, which is correlated with the measured output voltage ^¬ (U _A ), to the control ^¬ device (12); and c) by the control device (12): varying the switch-off time (T _out ) as a function of the measured output voltage (U _A ).